Temperature control mechanism



TEMPERATURE CONTROL ECHANISM Filed June 2, 1957 Patented Nov. 8, 1938 UNITED STATES PATENT OFFICE TEMPERATURE CONTROL MECHANISM Application June 28, 1937, Serial No. 150,768

11 Claims.

This invention relates to thermostatically controlled mechanism for use with electric. heating apparatus to switch a heating element on or off as may be required to attain and maintain a pre- 5 determined temperature in the apparatus, and myobject is to` devise mechanism of this character which will be cheap, simple and reliable.

I attain my object by providing a lever pivoted on a thermostatically actuated arm journalled i0 on a suitable stationary part. A switch arm normally tending to close a heating circuit is so connected with the lever at a point in alinement with the axis of the journal of the arm that, when the lever is rocked on its pivot, the switch arm l will be moved to open the circuit. As the temperature increases in the apparatus, the arm is moved to carry the lever into engagement with an adjustable regulator which causes the lever to rock relative to the arm and break the circuit when the temperature reaches the point indicated by the regulator. As the temperature in the apparatus drops, the movement of the arm is reversed and when the lever moves out of engagement with the regulator, the switch is again permitted to close. Thus the switch is alternately opened and closed as the temperature in the apparatus rises and falls respectively whereby the temperature is maintained substantially at the point set by the regulator.

30 The invention is hereinafter more fully described and is illustrated in the accompanying drawing in which- Fig. 1 is a front elevation of my control mechanism showing the switch for the heating circuit 35 closed;

Fig. 2 a similar view showing the switch opened;

Fig. 3 a section on the line 3-3 in Fig. 1; and

Fig. 4 a plan View of the switch arm and its 10 pivotal connections.

In the drawing like numerals of reference indicate corresponding parts in the diiierrent figures.

I is` a supporting plate for the various parts i5 and may be secured to any part of a wall or the top of an electrically heated oven. Carried by the plate I is a thermostatic element 2 of known type which requires no detailed description. To the rotatable spindle 3 actuated by the thermo- 50 static element is secured an arm 4. A lever 5 is pivoted at 6 intermediate its ends on the arm 4. `One end of the lever is provided with a lateral projection 1 which is normally positioned substantially in alinement with the axis of the spin- 56 dle 3. The otherend of the lever normally en- (Cl. 20o-138) gages a stop 8 on the arm 4 to normally position the projection 'l as aforesaid and to limit the rotary movement of the lever in one direction of rotation on its pivot.

A xed contact S is carried by a bracket I0 '5 secured at II to a block I2 of insulating material. The latter is secured by screws I3 to the plate I and is provided with terminal bolts I4, I5. One of the bolts is connected by a conductor I6 with the bracket I0. A movable contact I'I is` carried 10 by a switch arm I8 which normally maintains its Contact Il in electrical engagement with the xed contact 9. Preferably the switch arm I8 is rigid and is constantly urged to maintain its contact engaged with the fixed contact by a U 15 shaped spring frame I9. The frame I9 is pro- Vided with a lug 2D for securing it to the block I2 and with the arms 2| and 22. 'I'he free end of the switch arm I8 which carries the contact I 'I' extends through an opening in the arm` 2| 20 and the other end oi the switch arm is increased in width and has a knife-edge fulcrum against the inner side of the arm 2I on each side of the opening and a similar fulcrum against the adjacent end of a toggle member 23 which has a knifeedge fulcrum on the inner side of the other arm 22 of the frame I9.

The frame I9 maintains a spring tension against the end of the toggle member in the direction of its length and the various fulcra and a back-stop 24 are so arranged that the switch arm I8 is normally disengaged from the back-stop and its contact II is normally engaged with the contact 9. The back-stop 24 is adjustable in a bracket secured to the block l2 and is so adjusted relative to the fixed contact 9 that the toggle cannot be moved over center.

The toggle member 23 may be connected by a piece of insulation 25 and a spring 26 with the projection 'l on the` lever 5 whereby the latter, when rocked relative to the arm 4, causes the toggle member to move the switch arm contact I'I out oi engagement with the xed contact. The other terminal I5 is connected by a conductor 21 with the frame I9 so that a circuit including the lead-ins 28 will be broken when the contacts are separated.

An adjustable regulator comprising a pivoted abutment member 29, a cam 30, spindles 3I, 32 connected by a collar and set screws 33, a knob 34 having an indicator 35 and a calibrated scale 36 is provided for controlling the opening and closing of the circuit 28. The abutment member 29 is provided with a shoulder 3l adapted 55 to be engaged by a lug 38 on the end of the lever 5 remote from the projection l.

As the temperature rises, the arm 4 moves the lug 38 towards the shoulder 31 on the abutment member 29 which is held from movement by the cam 30. The continued movement of the arm and lever 5 as a unit results in the lug 38 engaging the shoulder 31 which causes the lever to rock on its pivot 6 away from the stop 8. The projection 'I is thus moved out of alinement with the axis of the spindle 3 to tension the spring 26 and cause the movable contact l1 to be moved out of engagement with the fixed contact 8. The heating circuit is thus broken but the temperature of the oven may rise slightly for a short period o time and, if so, the spring 26 will permit the arm 4 and pivot 6 to move relative to the lever lug 38 which is held from a continuing movement by its engagement with the shoulder 37. When the temperature of the oven drops suiciently to permit the lever 5 to return to its normal position the circuit will be again closed until the temperature of the oven reaches the point set by the indicator 35 on the scale 36.

Referring to Fig. 3 it will be noted that the cam 3S is so shaped that the higher the temperature desired in the oven, the greater the unitary movement of the arm 4 and lever 5 before the abutment member 29 is engaged by the lever. Referring to Figs. 1 and 2 it will be seen that the cam 30 engages the abutment member near its pivot 39 which enables the member to be iinely adjusted over a wide range with a minimum movement of the adjusting mechanism. If the device is used in a vertical position, a spring 40 may be employed to hold the member 29 in engagement with its cam 3D. This is not important, however, because the shoulder 31`wil1 not drop below the lug 38 and the Weight o the member 2S is not sufficient to affect the correct operation of the spindle 3 by the thermostatic element.

If desired a pointer and scale device could be readily connected with or operated from the spindle 3 for indicating the temperature of the oven. It is obvious that various modifications of the controlling means as shown and described could be made without departing from the spirit of my invention.

What I claim as my invention is:

1. Temperature control mechanism comprising a thermostatically actuated arm mounted to turn on an axis; a lever pivoted on the arm, the pivot of the lever being oiTset relative to the said axis; an adjustable regulator against which the lever is moved by the arm to cause it to rock relative to the arm; a switch arm normally closing a circuit; and means for connecting the lever, at a point substantially in alinement with the said axis, and the switch arm to move the latter to open the circuit when the levei` is rocked on its pivot.

2. Temperature c ontrol mechanism comprising a thermostatically actuated arm mounted to turn on an axis; circuit opening and closing means including a switch arm normally closing a circuit; lever pivoted intermediate its ends on the thermostatically actuated arm; and an adjustable regulator positioned for engagement by one end of the lever to cause it to rock relative to the arm, the other end of the lever, at a point substantially in alinement with the said axis, being connected with the switch arm so that the circuit will be broken when the lever ls rocked on its pivot.

3. Mechanism as set forth in claim 1 in which the connecting means includes a spring so that the arm is free to continue its turning movement after the lever has been rocked to cause the circuit to be opened.

4. Temperature control mechanism comprising a thermostatically actuated arm mounted to turn on an axis; a lever pivoted on the arm, the pivot of the lever being offset relative to the said axis; a pivoted abutment member adapted to be engaged by the lever to cause it to rock relative to the arm; a regulator for iimiting the movement of the said member in one direction, the regulator being adjustable to vary the distance through which the arm must move before the lever engages the abutment member; a switch arm normally closing a circuit; and means for connecting the lever, at a point substantially in alinement with the said axis; and the switch arm to move the latter to open the circuit when the lever is rocked on its pivot.

5. Temperature control mechanism comprisl ing a thermostatically actuated rotatable spindle; an arm secured to said spindle; a lever pivoted on the arm; an adjustable regulator against which the lever is moved to cause it to rock relative to the arm; a switch arm normally clos- ,rf

ing a circuit; and means for connecting the lever, at a point in alinement with the axis of the spindle, with the switch arm so that the latter will be moved to open the circuit when the lever is rocked as hereinbefore set forth.

6. Temperature control mechanism comprising a thermostatically actuated arm mounted to turn on an axis; a lever pivoted on the arm; an adjustable regulator against which the lever is moved by the arm to cause it to rock relative to the arm; a xed contact; a switch arm carrying a movable contact; means tending to move the switch arm so that its contact normally engages the xed contact; and means connected with the lever at a point in alinement with the said axis for actuating the switch arm to move its contact out of engagement with the xed contact when the lever is rocked on its pivot.

'7. rIemperature control mechanism comprising a thermostatically actuated arm mounted to turn on an axis; a lever pivoted on the arm, the

pivot of the lever being offset relative to the said axis; a pivoted abutment member adapted to be engaged by the lever to cause it to rock relative to the arm; means for engaging the abutment member close to its pivot to limit the movement of the said member in one direction, the means being adjustable to vary the movement of the arm before the lever engages the abutment member; a switch arm normally closing a circuit; and means for connecting the lever, at a point substantially in alinement with the said axis, and the switch arm to move the latter to open the circuit when the lever is rocked on its pivot.

8. Temperature control mechanism comprising a thermostatically actuated arm mounted to turn on an axis, a lever pivoted intermediate its ends on the arm, one of the said lever and arm parts having a stop for engaging the other of said parts to limitJ the rotary movement of the lever in one direction relative to the arm, one end of the lever having a lug extending laterally therefrom; a switch arm normally closing a circuit; and an adjustable regulator adapted to be en- CII gaged by the lug to cause the lever to be rocked relative to the arm; the other end of the lever at a point in alinement with the said axis being connected with the switch arm so that the circuit will be broken when the lever is rocked on its pivot.

9. Temperature control mechanism comprising thermostatically actuated means including an oscillatable arm; a lever pivoted on said arm; a switch arm; means tending to move the switch arm to close a circuit; an adjustable regulator adapted to be engaged by the lever to cause it to rock relative to the first mentioned arm; and means connected with the lever ot a point substantially in alinement with the axis of the oscillatable arm for actuating the switch arm to cause the circuit to be `opened when the lever is rocked on its pivot.

10. Temperature control mechanism comprising a. thermostatically actuated arm mounted to turn on an axis; circuit opening and closing means including a movable switch arm provided with a contact; a fixed contact; a back stop spaced from the fixed contact; a U shaped spring frame having two arms; a toggle member having one end pivotally engaging an end of the switch arm, the other end of the toggle member being pivoted on one arm of the U shaped frame, the switch arm being pivoted intermediate its ends on the other arm of the U shaped frame; a lever pivoted on the first mentioned arm; connections between the toggle member and a point on the lever substantially in alinement with the said axis; and an adjustable regulator adapted to be engaged by the lever to cause it to rock relative to the arm so that the toggle member will be moved to cause the circuit to be opened, the back stop being positioned relative to the xed contact to limit the movement of the switch arm so that the toggle member cannot move over center.

1l. Temperature control mechanism comprising a thermostatically actuated arm mounted to turn on an axis; an adjustable regulator; a member carried by the arm and movable relative thereto, the said member being adapted to engage the regulator to cause a movement of the member relative to the arm; a switch arm normally closing a circuit; and means connected with the member, at a point substantially in alinement with the said axis, for moving the switch arm to open the circuit when the member is moved relative to the arm to shift the said con- ,Y

nection out of alinement with the said axis.

ROBERT H. J. STARSMEARE. 

